In school, where I was taught “Castellano”, and I remember the word “mantequilla” (English: butter) as one of the vocabulary words. I have noticed that Spanish speakers from different geographic areas speak differently, slight differences in pronunciation, word usage, and maybe vocabulary. I have always heard the word “mantequilla” for butter.

I think it’s interesting that Babelfish translates butter as manteca and lard as manteca de cerdo or “pig butter!”

Right, Mantequilla is used in Spain as butter. Regarding Estampilla or Sello, I can tell you that in Spain no one uses Estampilla for “stamp”. The word is definitely “sello”. “Sello” also means “Seal” by the way.